The open throat, vertical chamber style of round baler has become the standard in the industry for variable chamber machines. Such machines operate on what may be described as a single-stage baling principle in which the bale is formed from beginning to end in the same chamber. Thus, at the start of a new baling cycle, incoming crop material is fed directly into the forming chamber instead of first entering into some kind of a small, precompression starting chamber beside or below the main chamber as in two-stage machines. In such two-stage machines, the incoming material during stage one at the beginning of a new baling cycle coils into a precompressed, relatively dense core within the small starting chamber before it then deflects a forming belt sufficiently to push its way into the main chamber, where it completes its formation in stage two.
The open throat, vertical chamber machine is an excellent starting machine because there is no attempt to coil or compress the crop material until it is first safely inside the baling chamber. It also starts well because of its vertical orientation at the beginning of a new baling cycle when an upwardly moving surface at the rear of the chamber lifts and tumbles the crop forwardly, while a downwardly moving surface at the front of the chamber lowers and coils the crop onto itself.
However, the chamber is supplied with material through a relatively wide, non-compressive inlet opening at the bottom of the chamber. Therefore, unless the starting material quickly forms into a coil that is larger than the width of the opening, there may be a tendency in some crop conditions for the downwardly moving material at the front of the chamber to come back down out through the opening. If it lands on the relatively skimpy, resilient rake tines of the pickup mechanism, the tines may not be strong enough to feed the mass of fallen material back up into the chamber. Consequently, the machine may plug.
In the past a starter roll has typically been provided at the bottom of the chamber in such a position that material coming down the front stretch of the chamber encounters the rearwardly rotating roll and is directed back toward the rear of the chamber, where it is picked up by the upwardly moving, rear surface and lifted upwardly with other incoming material. However, starter rolls have a tendency to wrap with crop materials in certain conditions and are also fairly expensive, considering not only the cost of the rolls themselves, but also that of the drives and bearings for the rolls.
Therefore, for many years there has been a long-felt need in the industry to find a way to eliminate starter rolls in open throat, vertical chamber machines. Yet, various attempts to solve this problem have produced only mixed results.